Train control



July 9, 1929. F. DODGSON TRAIN CONTROL Filed Nov. 20, 1

924 3 Sheets-Sheet 1 3.. mo Illllllllll Tl-l'l qww J mm AGE y 1929. F.L. oonesou 1.720.646

TRAIN CONTROL Filed Nov. 20, 1924 3 Sheets-Sheet 2 FIG.2.

July 9, 1929. 1 DQDGSQN 1,720,646

TRAIN CONTROL Filed Nov. 20, 1924 3 Sheets-Sheet 3 c 0 ml us 15 new. 81c 4 s1.

5 p48 as so EE'V,

Patented July 9, 1929.

UNITED STATES 1,720,646 PATENT OFFICE.

FRANK L. DODGSON, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAYSIGNAL COMPANY, OF ROCHESTER, N. Y.

TRAIN CONTROL.

Application filed November 20, 1924. Serial No. 751,120.

This invention relates to automatic train control systems for railroadsand more particularly to such systems of the continuous inductivecontrol type employing a 3-position relay on the train controllable togive any one of three different indications.

One of the principal objects of the present invention is to provideabsolute stop control for enforcing obedience to stop-and-stay interlocksignals, in addition to speed control for enforcing obedience to theindications of automatic block signals. In accordance with thisinvention, it is proposed to provide an auton'iatic brake applicationwhich occurs irrespective of the speed of the train and which can not beprevented by the engineer, whenever there is a change directly fromclear or proceed to stop or danger, without an intervening change tocaution. It is also proposed to provide such absolute stop control inaddition to the provisions for acknowledgment of caution and permissivestop signals.

Various specific objects, advantages and characteristic features of theinvention will be in part obvious and in part pointed out as thedescription progresses.

In the accompanying drawings, Fig. 1 shows in a simplified anddiagrammatic manner the trackway equipment of this invention forautomatic block signal territory, together with the impulse receivingdevices and a control relay for the locomotive or other vehicle,speed-distance curves of permissive speed limits, and interrupted linesfor indicating the points during the travel of the train at whichcertain contacts open and close;

Fig. 2 illustrates diagrammatically in perspective a simplifiedarrangement of operating gearing and associated parts, constituting aportion of the car-carried apparatus, this gearing and its controldevices providing for the operation of speeddistance contacts, anddistance contacts;

Fig. 3 illustrates diagrammatically and in accordance with somerecognized and some arbitrary conventions the various parts and devicesof the car-carried apparatus and their circuit connections; and

Fig. 1 illustrates how the trackivay equipment for automatic blocksignal territory, as shown in Fig. 1, is modified and organized toprovide for reduced speed control and absolute stop upon the approach toa stop-and stav interlock signal.

A specific organization of devices and circuits, selected to exemplifyone embodiment of the invention and herein shown and described, includesin some particulars structures and combinations, disclosed and claimedin prior applications filed by myself and others. For example, thespecific system herein shown and described, is similar to that disclosed in the Howe application, Ser. No. 746,578, filed October 29,1924, the present invention being in effect, generally stated amodification or adaptation of this type of system to incorporate thereinthe provision of it modified form of an absolute stop contro Traclcwagegm'pment.The trackway devices and control circuits for automatic blocksignal territory are the same as those of a continuous inductive controlsystem of the type using a 3-position car relay, with track phase andline phase circuits. Alternating current track circuits are illustratedin the particular form shown, but it should be understood that theinvention is applicable to direct current track circuits by employingthe well known expedients, such as shown in the Howe applicationmentioned above, for applying track phase and line phase train controlcurrents to direct current track circuits.

Referring to Fig. 1 there is shown a typical railway signaling system inwhich the track rails 1 are divided by insulating joints 2 into blocks,of which the block I and the adjacent ends of two other blocks H and Jonly have been shown. Since the various blocks are the same like partsof each block are designated by like reference characters havingdistinctive exponents. For simplicity it is assumed that the length ofthese blocks corresponds to braking distance and includes only one trackcircuit, various expedients (not shown) being employed to adapt thesystem to blocks of various lengths and those including cutsections. Atthe en-- trance end of the block I, the normal direction of traflicbeing as indicated by the arrow, is a track relay 3 of the alternatingcurrent type, this track relay being energized by current impressedacross the exit end of the block I by a track transformer 4 having itsprimary winding connected to the secondary winding of a transformer 5which receives its energy from a transmission line 6. Although traincontrol systems of the three-position inductive type such as the presentsystem, may be used in connection with trackway apparatus in which nowayside signals are used, signals of either the color light or semaphoretype may be used, and for convenience semaphore signals Z of thethree-position type have been shown without attempting to illustratetheir well known operating mechanism and control circuits.

The apparatus thus far described is that which is necessary for waysidesignal con trol purposes. In addition to this apparatus means areprovided for conducting an alternating current flowing in the samedirection in the two track rails in multiple and having a predeterminedphase relation with the track circuit current supplied by thetransformer at.

In the particular arrangement shown this simplex or line current iscaused to flow through. a circuit including the two rails in multiple byapplying alternating current potential to the two mid points otbalancing resistances bridged across the entrance end and exit end ofthe block respectively, which circuit may have its polarit reversed itthe block in advance becomes occupied. This simplex or line circuit maybe traced as follows:

Beginning at the secondary winding of the transformer 7 wires 8 and 9",front contact 10 of the track relay 3, wire 11, "to the mid-point ofbalancing resistance 12 through the two rails in multiple to theentrance end of the block 'I to the mid-point of balancing resistance13, wire 14%, front con tact 15 of the track relay 3 wire 16 back to thesecondary winding of the transformer 7. lVhen the track relay 3 isde-energized current is reversed in this circuit as is obvious bylooking at the pole changer contacts 10 and 15 Referring now to Fig. 4,which illustrates a continuation of the trackway apparatus shown in Fig.1, there has been shown the block K and the adjacent ends of the blocksJ and L of which the block ii is located in interlocking territory.Since many of the parts of the trackway apparatus shown in Fig. dare thesame as those shown in Fig. 1, such parts are designated by likereference characters having distinctive e.;ponents. It should be notedthat the signals Z and ZA are distant and home signals respectively tothe interlocking territory shown and for this reason these signals havebeen illustrated with square lades. The dotted rectangle shownillustrates an interlocking tower which among other things includes alever 27 which under normal stop condition, as shown, maintains thesignals Z :tHCl'ZA at the caution and stop position respectively in theabsence of a train in the block K, but it the block K is occupied thesignal Z will, of course, also indicate danger.

This lever 27 is suitably interlocked with levers of conflicting routes,such as, crossin sittings, etc. so that the signal ZA. which is anabsolute stop-and-stay signal must assumo the danger position before theswitch tor such siding may be opened or the derail for such crossing maybe closed. It may be mentioned at this time that the practice heretoforehas been to provide a derail just beyond a stop-and-stay signal, such asthe signal ZA, which was opened when the signal was stop so as to'assurethat a train would not pass such stop-and-stay signal when at danger. Inaccordance with the present invention it is proposed to eitect anautomatic brake application regardless of. speed instead of a derailmentwhen a train passes such a stop-andstay signal a. In addition to thebalancing resistances 19. and 13 heretofore mentioned there are providedbalancing resistances 2S and 29 in the block K, so that, a plurality ofsimplex circui are torn'ied. in order to readily see it these simplexcircuits are energized, normal or reverse, or are decnergized the leadsof the secondary winding of the trans iormer 7 have been i'narked plus(-t) and minus From this it will he noted that under absolute stop-an"tay conditions of the block K, as shown, the first section of thisblock is energized by reverse or caution current, that is, minus to plusfrom left to right, the second section is energized by normal. or clearcurrent, that is, plus to minus and the third section of this block hasits simplex circuit file-energized. Also, that when the lever 2'? isdepressed to its abnormal position the simplex circuit of the block l;is the same as that of the block H or l of block al territory; that is,is energized plus to minus under clear and is energized minus to plusunder caution tratlic conditions.

in the block H has been illustrated a typical railu'a j ehicle such asan engine and tender unit by wheels and axles l7 and 1.8. in tree t otthe first axle 17 ot the railway vehicle and directly over each trackrail are disposed car-carried elements comprising cores l9 having coils20 contained thereon. The cores 19 preferably are constituted oflaminated iron of high magnetic quality tern'iinating in enlarged polepieces. The coils 20 are connected in series so that voltages inducedtherein due to currents flowing in opposite directions in the two trackrails are cumulative and have bridged across leads leading therefrom acondenser 21 ot the proper capacity to resonate the coils 20 for thefrequency of the railway signaling current, so that the potential acrossthis condenser 21 is a maximum. These leads are connected to the inputside a track phase amplit 1; device All which includes suitable ampifying tubes of the vacuum t -Jpe, sources of energy, and tuningdevices, and whicn has its output leads con nected to the winding of amain relay h ll-l.

Similarly, cores 23 located in the rear of the lasttc-nder axle l8l'iave their coils 24- connected in series so that voltages inducedherein due to currents flowing in the same direction in the two trackrails in multiple are cumulative, the leads leading from these coilsbeing similarly resonated by a condenser 25, and through a line phaseamplifying device AL these coils are adapted to supply a current to theother phase winding of the main reh y R.

The main relay MR is preferably one of the induction type which willassume its normal position when the raiiway vehicle moves in a clearblock, in which tracltway and line phase currents are flowing which havea nor mal phase relation preferabiy misplaced suh stantially 9Oelectrical deg 'ecs; and obviously assumes the reversed position if thephase relation of one of these tracliway circuits is reversed andassumes the tie-energized position if one or both of these tracliwaycircuits are cut off.

The present invention has been shown in a system which contemplates agradual reduction in the permissive speed of the train as it passesthrough a caution block by the well known cam-and-governor arrangement,in which a permissive speet cam is driven in accordance with theprogress of the train through a caution block. Since thiscam-andgovernor speed control mechanism by itself does not constituteany part of the pr sent invention this mechanism wiil be briefly described, attention being directed to the application of V. K. Howe, Ser.No. 88,132 for a detailed description of such apparatus.

Referring to Fig. 2 this cam-and-governor mechanism diagrammaticallyillustrated is similar in many respects to that shown in the priorapplication to Howe Ser. 746,578 referred to. The shaft is driven fromthe wheels of the vehi cie in any suitabie manner and has a speedresponsive device or centrifuge O of the well known centrifugal typemounted thereon. It is obvious from the drawings that the grooved collar31 of the speet responsive device O moves downwardly as the speed of thetrain increase Adjm cent the shaft 30 and preferably at right anglesthereto is a speed shaft 82 which has a bifurcated arm 33 pinned theretoof which suitable pins extending inwardly from the bifurcated end ofthis arm engage the groove in the conar 31, so that the shaft 32 isrocked to a position depending on thespeed of the train. On this speedshaft 32 is secured a sector 34 which is adapted to close contacts 35when the speed of the train is below 15 miles per hour, as indicated bythe legend in Fig. 3.

On the shaft 30 is also suitably secured a worm 36 which is incontinuous meshed engagen'icnt with a worm wheel 87 secured to theshaftwhich shaft has a pinion 3ipinned thereon. The pinion 39continuously meshes with the gear a0 pivotaily SUPPOliGfl on a journal41. This journal 41 also pivotally supports the bifurcated end of an arm42 which arm straddles the gear and has a pinion 43 journaled thereinwhich is in con tinued mesh relation with the gear 40. This arm i2 urgedupwardly by a spring So as to tend to place the pinion 43 into meshedrelation with the mutilated gear L5. Under normal ciear trafiicconditions, however, this arm &2 is held in its lower position, asshown, by a cam starter magnet HOS.

The mutilated gear 4-5 is fastened to the high cam shaft i6, this shaftbeing held in its normal position by a spring 49 engaging the free endof the arm secured to this snaft 16. On the shaft 46 is contained a distance cam 4'7, which is adapted to operate co tacts as at a pointdepcndii'lg on the distance the train has traveled since the cam startermagnet HOS was tic-energized as more clearly pointed out hereinafter.

To the speed shaft 32 is suitably secured an arm 51 to the free end ofwhich is pivotally connected floating lever 52, which lever has its freeend bifurcated and provided with a roller 53 engaging the surface of apermissive speed am 50.. Obviously, since the arm 51 responds to thespeed of the train and the cam 50 is shaped to move the roller 53, toset up permissive speed limits as the train proceeds with the camstarter magnet HOS deenergized, all that is necessary to open contactswhen the actual speed of the train is too high as compared with thepermissive speed is to cause lese contacts to respond to the movement ofan intermediate point on the floating lever 52. In the particulararrangement shown a sector 5% pivotally supported by a journal 54 isprovided, which sector has an eccentricaliy located pin 56 connected toan intermediate point of the floating lever by a link 57., so that thissector is rocked toward the right as the speed increases and also as thetrain progresses, so that the speed must be reduced as the trainprogresses through the block. This sector 5; is biased in a counterclockwise direction by a spring 58 so to hold the roller 53 against thecam 50. This sector 5% permits opening of the outwardly biased contacts59 when the speed of the train is excessive. In a similar manner the iowcam shaft 46* for operating distance contacts only is provided. whichshaft is turned in accordance with the progress of the train when thelow cam starter magnet LOS is tie-energized, and since various parts ofthese devices are the same like reference characters with distinctiveexponents a have have been applied to such parts of the low cam. shaftmechanism.

Referring now to Fig. 3 of the drawings, there has been shown inaddition to the apparatus already referred to mechanism including anacknowledging relay A0]; R, a penalty relay PR. and an electro-pneumaticvalve EPV. The two reiays ust mentioned may be of any suitable type, butare preferably conpneumatically op rated brake control device,

which device is adapted to vent the brake pipe to a predetermined extentin a manner so that the engineer cannot recharge the same, or is adaptedto control a brake valve actuator for operating the usual cngineersbrake valve to the service position in a manner so that the engineercannot prevent such automatic operation of the brake valve.

Fig. 8 shows the electrical connections between the various devices ofthe car apparatus; and in this circuit plan, various conventions havebeen adopted to simplify the illustration and facilitate explanation.The vari ous contact fingers of the various relays are shown directlyunder the conventional illustration of the relay controlling them andare connected by dot and dash lines. Each distance shaft is similarlyillustrated by a dot and dash line leading to the cam-starter magnetgoverning the same.

In order to facilitate the description of the various circuit changesthat take place in the car-carried circuit arrangement shown in Fig. 3it is considered advisable to trace the normally closed circuits first,after which the circuit changes may be considered as the train proceedsunder various speed and trafiic con ditions.

The high cam starter magnet HCS is normally energized by the batterytl'irough a circuit including the contact 61 of the main relay MR whenthis relay is in its normal clear traiiic position, which circuit isreadily traced in the drawings. Similarly the low cam starter magnet LCSis energized if the main relay MB is either in its normal or itsreversed position through the following circuit :beginning at the busbar 62 connected to one side of the battery 60, wire 63, contact 64- ofthe main relay MR, wires 65 and 66 depending on whether the relay MRassumes its normal or reversed postion, wire 6?, wind ing of the low camstarter magnet LCS, wire 68, push button PB, wire 69 to the other bus 70connected to the other terminal of the battery 60. With the cam startermagnets HUS and LCS energized the distance shafts L6 and L6 assume thenormal position as shown in F 2.

Under clear traiiic conditions as illustrated the penalty relay isenergized by the following stick. circuit :beginning at the bus 62, wire71, contacts 48 operated by the distance cam 17, wires 108, 72 and 78,distance contact 48 operated by the distance cam ll, wires Ti, 75, 7 6and '57, front contact 78 of the penalty relay PR, wires 7 9 and 80,winding of the penalty relay PR, wire 81 to the other bus 70. It shouldbe noted that the penalty relay PR is also energized under clear tratliccondi tions by a circuit including contact 82 of the main relay MR whichis readily traced in the drawings and includes the greater part of thecircuit just traced. The purpose for which this circuit has beenprovided is more readily pointed out hereinafter. T he device EPV isnormally energized through the following circuit :Starting at the bus62', wire 83, cam and governor contacts 59, wires 8%, and 85, distancecontacts 86 operated by the distance cam 87, wires 88 and 89, frontcontact 90 of the penalty relay PR, wire 91, winding of the EPV, wire 92to the bus 70.

Operation in block signal territory By looking at the circuit for thedevice EPV just traced it readily appears'that this device is(lo-energized if either the penalty relay PR is (lo-energized, the speedof the train is in excess of the speed set up by the permissive speedcam 50 as manifested by the opening of contacts 59, or if the contacts86 of the cam 87 are open while the contacts 35 of the speed cam 34 areopen due to the train speed being above 15 miles per hour.

In order to facilitate explanation, let us assume that the train inquestion equipped with the car apparatus shown in Fig. 3 in its normalcondition is moving from left to right in the block H when the block Iin advance thereof is a caution block, that is, with the block Iunoccupied and the block J occupied by another train. So long as thetrain moves in a clear block only a certain maximum speed restriction isenforced which for the particular cam shown is 60 miles per hour asindicated by the curve 93 in Fig. 1 of the drawings. If the trainexceeds this speed at any time an automatic brake application occurs,after which brakes may again be released by the engineer as soon as thespeed is no longer excessive. As the train in question enters the blockI the alternating current impressed on the winding 26 of the main relayMB- is reversed, because the line phase circuit in the block I has itspolarity reversed by reason of dropping of contacts 10 and 15 of thetrack relay 3. This causes the main relay ME to swing its contacts 61,6% and 82 to the left, thereby file-energizing the high cam startermagnet HCS and opening one of the circuits heretofore mentioned forenergizing the penalty relay PR, namely, the circuit including thecontact 82 of the relay MR, this relay PR- howe ver still beingmaintained energized through the other cireuitwtraced. lVith the highcam starter magnet HUS deenergized the high cam shaft 46 is graduallyrotated, thereby decreasing the permissive speed of the train graduallyas indicated by the curve 93 in Fig. 1 of the drawings. After a shortdistance of movement in the caution block the distance cam 94 closescontacts 95, as indicated by the solid portion of the line 95 in Fig. 1of the drawings thereby closing a circuit which sounds the acknowledgingsignal A01: S by the energization ot the following circuit :beginning atthe bus 02, wires 96 and 97, acknowle lging signal Ac]: S, wire 98, backcontact 99 of the acknowledging relay A070 R, wires 100 and 101,contacts 5 operated by the distance cam 94, wires 102' and 103 to theother bus 70. The sounding of this acknowledging signal informs theengineer that he must perform an acknowledging act to show his Vigilanceand in turn avoid an automatic brake application. If the engineer nowpresses the acknowledging push button PB a pick-up circuit for theacknowl edging relay Ae ie R is completed, which may be traced asfollows:beginning at the bus 62, wires 90 and 10%, winding of theacknowledging relay A070 R, wires 105 and 106, push button PB, wire 69to the other bus 70. It should be noted that with this acknowledgrela'A015 R energized, the circuit for energizing the acknowledging signalAck S is broken. lVith this relay Ac/e R once picked up a stick circuitfor this relay is completed as follows :-beginning at the bus 62, wires98 and 101, winding of the acl-tnowledging relay Ada R, wires 105 and107, front contact 99 of the relay Ada, wires 100, and 101, distancecontact 95, wires 102 and 103 to the other bus 70.

Aft r the train has proceeded a little further the distance contacts 18operated by the cam 17 are opened for a short distance of travel asindicated by the interrupted portion of the line 418 in Fig. 1 of thedrawings. The opening of contacts 4:8 breaks the stick circuit for thepenalty relay PR heretofore traced which includes these contacts 18, butsince the engineer has manifested his Vigilance by depressing the pushbutton PB and sticking up the acknowledging relay Ada R, an auxiliarystick circuit for the penalty relay PR is completed, which may be tracedas follows :beginning at the bus 62, wire 71, contacts eh operated bythe distance cam 17, wires 108 and 109. front contact 110 of theacknowledging relay Ads E, wires 111 and 112 and 77, front contact 78 ofthe penalty relay PR, wires 79 and 80. winding of this rela PR, wire 81to the other bus '70.

After another short distan e of travel of the train the contacts 18 areclosed and the contacts 95 are opened. The opening of con tacts caus sdropping of the acknowledging relay Ac]; R so as to again place it inits normal condition. As the train proceeds through the block I theengineer is obviously required to reduced his speed as indicated by thecurve 93 to avoid an automatic brake application by opening of thepermissive speed contact 59.

Near the end of the block I the distance shaft 16 will have reached itsultimate position wherein the pinion 43 engages the mutilated portion ofthe mutilated gear 45, after which the permissive speed is constant asiudicated by the horizontal line 113 (see Fig. 1). Also us" before thehigh cam shaft d6 reaches its ultimate position the contacts 114operated by the distance cam 115 are closed indicated by the solidportion of the line 11% in Fig. 1 of the drawings. The closing of thesecont: is does not complete a circuit but permits another auxiliaryacknowledging circuit to be completed as more clearly pointed outhereinafter.

As the train proceeds into the block J, which is assumed to be occupiedby said another train, no track phase current can be detected in theelements located in front of the first axle of the train because thiscurrent is shunted away by said another train in advance. This causesthe main relay MR to assume its de-ener ized position so as to (lo-enerize the low cam starter magnet LCS. With tars cam starter magnet LCSde-energized the low cam is gradually rotated in acc rdance with theprogress of the train and .fter a short distance of movement of the thecontacts are closed, as indicated the line 95 in Fig. 1, thereby againsounding the acknowledging signal Ads S through a circuit which isobvious from the drawings. The sounding of the acknowledging signal A070S advises the engineer that he must dopress the push button PB tomanifest his vigilance and that he is now entering an occupied block.Depression of the push button PB again picks up the acknowledging relayAct: which relay after once piared up is stuck up through the same stickcircuit heretofore traced except that the present circuit includescontacts 95 and not 95.

Upon a slight further movement of the train in the occupied block thecontacts 48* are opened as indicated by the horizontal line 1-8 (seeFig. 1) which interrupts the stick circuit for the penalty relay PRheretofore traced. The penalty relay is, however, not (lo-energizedbecause it is now energized through tne following circuit :beginningatthe bus 62, wire 118, contacts 114 operated by the distance cam 115,wire 119, front contact 120 of the penalty relay PR, wires 121, 112 and77, front contact 78 of the penalty relay PR, wires 79 and 80, windingof the penalty relay PR, wire 81 to the bus 70. In other words, theengineer has avoided de-energization of the penalty relay PR bydepressing the push button PB in response to the acknowledging signalAclc S. At about the same time that contacts 48 open the contact 86 ispermitted by the cam shaft 46* to also open, as indicated by the line 86in Fig. 1 of the drawings. With the contacts 86 open the device EPVrelies for its energizing current upon the continuity of the circuitthrough speed contacts 35 which are only closed if the speed of thetrain is less than say, 15 miles per hour.

At first hand it would appear that the con tacts 35 and 86 areunnecessary, because the contacts 59 are already open if the speed ofthe train is over 15 miles per hour under the assumed conditions. Thereare however conditions where this is not true and these contacts 35 and86 are essential. For instance, assume the train to be moving at a. veryslow speed near the end of a block and a switch is opened in the blocknext in advance; under this condition the high cam would not yet havebeen run d wn when the train reaches the end of the block and under thiscondition the contacts 35 would set up the restricted speed limit.

It may be stated at this time that contact 82 of the main relay MR hasprincipally been provided to prevent the requirement of acknowledgmentwhen either the high or the low cam shaft are restored to their normalposition, during which time the contacts 48 or 4:8, as the case may be,are open; and it will be noted that these contacts are shunted by thecontact 82 during the restoration of these cam shaft's, so the penaltyrelay is not dropped. For instance, if traffic conditions change fromdanger to caution (both the high cam l7 and the low cam 47 in therun-down position) movement of the contact 82 from its neutral to itsleft-hand position closes the following circuit for the penalty relay PRbeginning at the battery 60, bus wire 62, contact 82 of the main relayMB in its left-hand position, wire 73, contacts 48 of the high distantcam ll, wires 74;, 75, 76, and 77, stick contact 78, wires 79 and 80,windin of the pen alty relay PR, wires 81 and back to battery 60.Momentary opening of contacts 48" due to reenergization of the camstarter magnets LCS will not effect deenergization of the relay PR byreason of the presence of the auxiliary circuit just traced. Also,change in traiiic conditions from danger or caution to clear will notpermit deenergization of the penalty relay PR even though contacts 48are momentarily opened because the following auxiliary circuit is firstclosed :beginning at the battery 60, wire 62, contact 82 of relay MRassuming the right-hand position, wires 76 and 77, stick contact 78 ofthe penalty relay PR, wires 79 and 80, winding of the penalty relay PR,wires 81 and 70 back to battery 60. When either of these cams isrestored to its normal position the acknowledging signal Ac /c S ismomentarily sounded; since this momentary sounding of the signal canreadily be distinguished from the sound ing when acknowledgment isrequired it may be used to inform the engineer that a favorable changein traffic conditions has taken place. The difference in the time duringwhich this signal sounds when the cams are run down and restoredrespectively, is due to the fact that these cams are driven slowly fromtheir normal position and are almost instantly restored by the spring 47or 47 to the normal position. It should be noted that the push button PBis protected against misuse, that is, it cannot be permanently tieddown, for by so doing the cam starter magnet LCS is tie-energized andthe minimum speed limit of 15 miles per hour is immediately thereafterset up and continues so long as this push button is tied down.

From the above it appears that the engineer is required iTOlnZlliB anacknowledging act when achange of traffic conditions from clear tocaution takes place, and also when a change of traftic conditions fromcaution to danger takesplace.

Operation at the approach to a st0p-cmcZ- sf'ag S';:II ((Z.LOiI us nowconsider the movement of a train during its approach to a stop-and-staysignal. Let us assume that a train equipped with the car-carriedapparatus shown in Figure 3 enters the block K when a conflicting routeis set up that is, the lever 27 is in normal position and the tower mancannot change this lever from its normal position. As the train entersthe block K, consequently the engineer is required to acknowledge thischange in traffic conditions and thereafter is required to restrict hisspeed in accordance with the permissive speed limit set up by the cam50, as shown by the curv 93 in Fig. 1, so that the train has practicallyreached its minimum speed of 15 miles per hour when it reaches thebalancing resistance 28. As heretofore mentioned, the section betweenbalancing resistances 28 and 29 is provided with simplex current ofnormal polarity so that the relay MR- is again energized to its normalposition for a short distance 7a of movement as indicated in the blockK. This restores the high cam to its normal position, and as the trainproceeds in the face of the absolute stop-and-stay signal ZA at danger,and passes beyond the balancing re sistance 29, a sudden change fromclear to danger takes place because there is not simplex circuit currentpresent between the balancing resistances 29 and 12 so that, the relayMR- changes from its normal to its deenergized position abruptly. Thischange of the main relay MR causes both the high cam shaft 46 and thelow cam shaft l6 to be started at the same time, and after a shortdistance of movement the acknowledging signal A070 S is sounded forreasons heretofore given. Even if the engineer now presses the pushbutton PB for reasons heretofore given, this will avail him nothinbecause the contacts 114 have notyet closed, so that,

the circuit for maintaining the penalty relay PR up including thiscontact 114 and the contact 120 of the acknowledging relay hell: is notcomplete at the time contacts 48 and 48 are open; and this relay PR istie-energized and an automatic'brake application occurs. It is assumedthat this brake application is suflicient warning to the engineer thathe will not continue movement of his train after it has been brought toa stop.

The distance contact cams a7 and 1" are preferably so designed that thecontacts 48 and a8 will have been reclosed before the train has beenbrought to a stop by the auto matic brake application just mentioned,and as soon as the train has been brought to a stop, a pick-up circuitfor the penalty relay PR is completed which may be traced as followsz-beginning at the positive bus 62, wire 71, contacts 48 and 48, wire7%, contacts which are only closed when the train is substantially at astop, wires 123 and 80, winding of the penalty relay PR, wire 81 to thenegative bus 70. The completion of this circuit obviously causes thepenalty relay to assume its attracted position after which the stickcircuit is completed and the penalty relay PR is again stuck up, so thatthe engineer may proceed if he desires to do so. The engineer will, ofcourse, not proceed until the stop-and-stay signal ZA, assui'nes itsclear position, which it will as soon as the tower man changes the lever27 controlling this signal to its abnormal proceed position, it beingassumed, of course, that traflic con-v ditions ahead are clear.

In order to assure that a change from clear to danger takes place at theapproach of the train to an absolute stop-and-stay signal. the trackwaycircuits necessary to energize the relay HR to its clear position may bechecked in any one of the well known ways, for instance, the wireleading to the midpoint of balancing resistance 29 may have a checkrelay therein which must be energized before a conflicting route can beset up, so that the possibility of a failure of proper operation of theabsolute stop mechanism is very remote.

A train control system embodying the present invention has certainadvantages over other train control systems of the continuous inductivetype having absolute stop features incorporated therein heretoforeproposed, in that, a failure of trackway energy by reason oftransmission line trouble, or the like, merely effects a brakeapplication regardless of speed after which the train may again proceedat the discretion of the engineer.

Although in the simplified train control system shown, no specific meanshas been shown for cutting out the automatic apparatus when the trainenters the territory not equipped for train control, it is to beunderstood that suitable apparatus for this pur pose is in mostinstances necessary. If such means is to be employed in a systemembodying the present invention it is proposed to employ the arrangementfor picking up a non-control territory stick relay disclosed in theapplication of C. S. Bushnell, Ser. #723,048 filed June 28, 1924, towhich reference may be made for this purpose.

Having thus shown and described one rather specific embodiment of thepresent invention and having shown it applied to a simple alternatingcurrent block signal system, it is desired to be understood that thespecific apparatus illustrated has been selected for the purpose ofdisclosing means for carrying out the invention rather than for thepurpose of illustrating the particular apparatus preferably employed inpractice or the scope of the invention, and that various changes,modifications and additions may be made to adapt the invention tovarious other types of railway signaling systems or to systems in whichno wayside signals are used and suitable cab signals controlled by themain relay MR are employed, all without do arting from the scope of theinvention or the idea of means underlying the same.

What is claimed as new and desired to be secured by Letters Patent is 1.Gar-carried apparatus for automatic train control systems comprising,two delayed action devices one of which is initiated upon a change or"tratlic conditions from clear to caution and the other of which is initi;ed upon a change from caution to danger, means for restricting thespeed of the train differently when one or the other of these devices isinitiated, and means for effecting an automatic brake applicationregardless of the speed of the train if both of said delayed actiondevices are initiated simultaneously.

2. Car-carried apparatus for automatic train control systems comprising,means for restricting the speed of the train to a given limit upon achange of traflic conditions from clear to caution, means for furtherrestricting the speed of the train to a lower limit in response to achange in traiiic conditions from caution to danger, and means forstopping the train regardless of speed only upon an abrupt change oftrafhc conditions from clear to danger.

3. Car-carried apparatus for automatic train control systems comprising,brake applying means for effecting a brake application it a change oftratlie conditions from clear to caution, from caution to danger or fromclear to danger takes place, manually operable acknowledging means whichif actuated when a change of trafiic conditions from clear to caution orfrom caution to danger takes place prevents a brake application by saidbrake applyin means but which is incapable of preventing a brakeapplication it operated when a change of tratiic conditions from clearto danger takes place.

4. Car-carried apparatus for automatic t'ain control systems comprising,means for giving); a signal and for etlccting a bralre application it achange of tratlic conditions from clear to caution, from caution todanger or from clear to danger takes place, manually operableacknowledging; means which it actuated immediately atte said signalgiven prevents a brake application by said first mentioned means 113011a change from clear to caution or caution to danger but which isincapable of preventing a l alto application if Opfiltlttl when a signalis given in response to a c u nge of traiiic conditions from clear todancer.

5. In an automatic train control system; the combination of car-carriedapparatus comprising, an electroresponsive device adapted to assumethree different positions in response to clear, caution and dangertratlic conditions ahead respectively, means for restricting the speedof the train upon a change in traffic conditions from clear to cantion,another means for restricting the speed of? the train upon a chai'ige intratlic conditions from caution to danger, and means for effecting abrake application regardless of train speed when a change in tratlicconditions from clear to danger takes place; and of trackway apparatusat the approach to a stop-and-stay signal tor causing said relay tochange from clear to danger as the train approaches said stop-and-staysignal thereby stopping the train upon its approach to such signalregardless of the speed of the train at the time.

6. In an automatic train control system for railroads; the combinationof car-carried apparatus including a slow acting device char ing inaccordance witl the progress of the vehicle when active and initiatedupon a change in tratlic conditions from clear to caution, anothersimilar slow acting device initiated upon a change in traiiic conditionsahead from caution to danger, a manually op rable device, means forcheating an auto 'c bralqe application when either of said devices areinitiated unless said man .ally operable device is operated and edectiveto automatically apply the brakes regardless of tie operation of saidmanually operable device when both of said slow acting devices areinitiated simultaneously; and of tracl-:- way means at the approach to astopand-sta signal for manifesting on the car tratiic conditionscorresponding to a change from clear to danger the car approaches saidsignal, thereby effecting a brake application regardless 0i whether ornot the engineer operates said manually operable device.

7. In an automatic train control system for railroads; the combinationof car-carried apparatus including a slow acting'device changing inaccordance with the progress of the vehicle and initiated upon a changein tratiic conditions from clear to caution, another similar slow actingdevice initiated upon a change in tratfic conditions ahead from cautionto danger, a manually operable de ice, means for reflecting" anautomatic brake application when the train traveled a predetermineddistance after either of said devices are initiated unless said manuallyoperable device is operated and effective to automatically apply thebrakes regardless of the operation of said manually operable de ice whenthe train has traveled a pred termined distance after both of said slowacting devices are initiated simultaneously; and 0t trackway meanslocated at the approach of a stop-and-stay si nal for manifesting on thecar traiiic condi tions corresponding to a change from clear to dangerwhen the car ap 'iroaches said signals, whereby an automatic brakeapplication is ciiected regardless of whether or not the engineeroperates said manually operable device after the train has traveled saidpredetermined distance with both of said slow acti Q devices initiated.

S. in an automatic train control system, tratlic controlled trackwaymeans for transmitting influences corresponding to traiiic conditions toa moving vehicle, such influences changing trom clear to caution andfrom caution to danger in response to increasingly unfavorable tratiicconditions ahead, and changing from clear to danger at certain pointsalong; the trackway where a stop is required, car-carried apparatuscomprising means for restricting the speed of the train to a given limitupon a change of said influences from clear to caution, means forfurther restricting the speed of the train to a lower limit in responseto a change of said influences from caution to danger, and means forstogping the train regardless of speed only upon a chan e of influencesdirectly from clear to aautomatic train control system, trafficcontrolled track ray means for producing on a moving vehicle threeoitierentsig nal impulses in a given scruieuce under certain t aclrwayconditions, and for producing a diti erent sequence of impulses underother trackway conditions, car-carried means responsive to said impulsesfor producing a given degr e of control in response to said givensequence of impulses and responsive irrespective of manual control forproducing a different degree of control in response to said differentsequence of impulses.

10. In an automatic train control system, car-carried apparatuscomprising means for restricting; the speed of the vehicle upon thereception of three distinctive signal impulses in a given sequence, andmeans for stopping the train. only upon the reception of two of saidsignal impulses in a different sequence.

11. In an automatic train control system, car-carried apparatusincluding means for giving a permissive stop control of the car uponreception of at least three distinctive signal impulses in a givensequence, and an absolute-stop control of the car upon reception ofimpulses in a different sequence.

12. In an automatic train control system, car-carried apparatusincluding means for giving a permissive stop control of the car uponeach change of at least three received distinctive signal impulses in aconsecutive order of less to more restrictive character.

and an absolute stop control of the car upon change of impulses in anon-consecutive order.

13. In an automatic train control system, traffic controlled trackwaymeans for producing on a moving vehicle at least three different signalimpulses in a given sequence, traflic controlled trackway means forproducing a different sequence of impulses, and car-carried meansresponsive to said impulses for giving a permissive stop control inresponse to said given sequence of impulses and for giving an absolutestop control in response to said different sequence of impulses.

In testimony whereof I afiix my signature.

FRANK L. DODGSON.

